Global warming is so last year. Lawrence Bender — who produced “An Inconvenient Truth” and won a Nobel Peace Prize for Al Gore — has a new cause: nuclear proliferation. Bender, who produced “Pulp Fiction” and “Kill Bill” before his conversion to agit-prop, is about to release “Countdown to Zero,” a documentary by talented British filmmaker Lucy Walker, which argues that nuclear devastation is more likely now than during the Cold War because of terrorism and the theft of weapons-grade uranium. At Coralie and Dennis Paul’s “React to Film” screenings at Soho House on Monday night, Bender and Walker were joined by glamorous ex-CIA agent Valerie Plame in calling for all the nuclear powers to destroy their 23,000 warheads, even as Iran is trying to build new ones. Fat chance. But the documentary — with interviews of Mikhail Gorbachev, Jimmy Carter and Zbigniew Brzezinski — is sure to win an Oscar for its high-minded, good intentions.